Separation media and methods especially useful for separating water-hydrocarbon emulsions having low interfacial tensions

ABSTRACT

Separation media, separation modules and methods are provided for separating water from a water and hydrocarbon emulsion and include a fibrous nonwoven coalescence layer for receiving the water and hydrocarbon emulsion and coalescing the water present therein as a discontinuous phase to achieve coalesced water droplets having a size of 1 mm or greater, and a fibrous nonwoven drop retention layer downstream of the coalescence layer having a high BET surface area of at least 90 m 2 /g or greater sufficient to retain the size of the coalesced water droplets to allow separation thereof from the hydrocarbon.

CROSS-REFERENCE

This application is a continuation of commonly owned co-pending U.S.application Ser. No. 12/576,839, filed 9 Oct. 2009, the entire contentsof which is hereby incorporated by reference.

FIELD

The embodiments disclosed herein relate generally to separation mediaand methods for separating water-hydrocarbon emulsions. In especiallypreferred forms, the embodiments disclosed herein relate to separationof water from a water-hydrocarbon fuel (e.g., diesel fuel) emulsion.

BACKGROUND

The need to separate emulsions of water and hydrocarbons is ubiquitous;historically impacting a broad array of industries. The separation ofwater-hydrocarbon emulsions has conventionally involved systems thatrely on single or multiple elements, novel flow patterns, stillingchambers, parallel metallic plates, oriented yarns, gas intrusionmechanisms, and electrostatic charge. The balance of separation systemsemploy an element that contains a fibrous, porous coalescing mediathrough which the emulsion is passed and separated. Irrespective of thesystem design, all water-hydrocarbon separation systems target thecollection of emulsified drops into close proximity to facilitatecoalescence. Coalescence and subsequent separation due to densitydifferences between water and hydrocarbons is the mechanism behind allseparation systems.

Conventionally known fibrous, porous coalescence media induce emulsionseparation in flow-through applications through the same generalmechanism, irrespective of the nature of the emulsion. The coalescencemedia presents to the discontinuous phase of the emulsion anenergetically dissimilar surface from the continuous phase. As such, themedia surface serves to compete with the continuous phase of theemulsion for the discontinuous, or droplet, phase of the emulsion. Asthe emulsion comes in contact with and progresses through the coalescingmedia, droplets partition between the solid surface and the continuousphase. Droplets adsorbed onto the solid media surface travel along fibersurfaces, and in some cases, wet the fiber surface. As more emulsionflows through the media, the adsorbed discontinuous phase encountersother media-associated droplets and the two coalesce. The dropmigration-coalescence process continues as the emulsion moves throughthe media.

A coalescence media is therefore typically considered to be functionallysuccessful for breaking a given emulsion if the discontinuous phasepreferentially adsorbs or is repelled and if the droplet phase has beencoalesced into drops at the point of exit from the media that aresufficiently large to allow their separation from the continuous phase.Typically, the drops separate from the continuous phase as a function ofdensity differences between the liquids involved. Conversely, acoalescence media is considered to be functionally unsuccessful forbreaking an emulsion if the drops remain sufficiently small at the pointof exit from the media that they remain entrained by the continuousphase and fail to separate.

Conventional fibrous, porous coalescence media are known whicheffectively remove over 90 wt. % of emulsified water from a hydrocarbon,when the hydrocarbon has an interfacial tension (γ) above 25 dynes/cmwith water. If the hydrocarbon displays hydrocarbon-water interfacialtension below 25 dynes/cm (colloquially known as “sub-25 interfacialtension hydrocarbons”), the water-hydrocarbon emulsion is considerablymore tenacious and the ability of prior art emulsion separation media toremove emulsified water diminishes dramatically to the point where40-100 wt. % of emulsified water is allowed to pass into the end usewithout removal.

A decrease in hydrocarbon interfacial tension occurs when thehydrocarbon is dosed with surfactants. In this regard, one root cause ofprior art fibrous, porous coalescence media failure in sub-25interfacial tension hydrocarbons is the presence of increasedsurfactancy. In cases of sub-25 interfacial tension hydrocarbons,emulsion separation requires more complex systems that often involvenested pleated elements, flow path controllers, wraps, and stillingchambers. The prior art is replete with examples of complex systemsdesigned to manage difficult to separate water-hydrocarbon emulsions.Therefore the need for a universal media capable of emulsion separationirrespective of hydrocarbon-water interfacial tension or surfactantcontent is clear in the face of such complexity.

The role of surfactant-deactivation of conventional fibrous, porouscoalescence media includes drop size, drop stability, and surfaces.Surfactants are molecules that contain both hydrophilic and hydrophobicmoieties. When present in a hydrocarbon-water mixture, surfactants alignat interfaces with the hydrophilic head group associated with thewater-like phase, and the hydrophobic tail extended into the oil-likephase. This is the lowest energy conformation of the surfactant, and itresults in depressed hydrocarbon-water interfacial tension. As a resultof depressed interfacial tension, a given increment of input energy tothe hydrocarbon-water mixture will result in a higher interface surfacearea in the presence of a surfactant. Interface surface area isinversely proportional to discontinuous phase drop size. Thus, in thepresence of surfactant, a given increment of input energy will result ina smaller drop size distribution of discontinuous phase than in theabsence of surfactant. In this regard, all fuel-water separation mediarely on physical interaction between water drops and the media to effectseparation. Surfactants create sufficiently small water drops that manypass through the media without encountering it. Surfactants alsostabilize the emulsion from separation so that drops that do impact themedia are less likely to partition out of the fuel onto the media.Similarly, drops that impact other drops resist coalescing into thelarger drops necessary for successful separation. Finally, surfactantsassociate with surfaces of media and water drops, and interfere with theunique surface interactions between media and water that destabilizewater within the fuel and allow its separation. Collectively, the resultof blending surfactants into a hydrocarbon is deactivation of the priorart fibrous, porous coalescence media and escape of water into the enduse.

The need for a fibrous, porous coalescence media that removes waterindependent of hydrocarbon interfacial tension has become substantiallymore pronounced with mandated changes in diesel fuel quality. In the2007 Heavy Duty Highway Diesel Rule, the EPA mandated respectivereductions of particulate (PM2.5) and nitrogen oxide (NOx) emissions of90% and 92%, with NOx allowances to drop an additional 3% in 2010. Atthe time of the mandate release, sulfur sensitive exhaustafter-treatment was considered necessary to meet 2007 emission goals. Asa result, the 2007 Highway Rule also requires sulfur levels in dieselfuel to drop 97% to 15 ppm. The resulting ultra low sulfur diesel fuel(ULSD) has been stripped of its native lubricity and requires surfactantaddition to meet engine wear control requirements. ULSD consistentlymanifests sub-25 interfacial tension hydrocarbons with water. EPAmandated diesel fuel requirements will cascade into off-road diesel,rail, and marine fuels as part of the EPA's tiered approach to emissioncontrol, indicating all non-gasoline transportation and power generationfuels will converge over time at sub-25 dynes/cm interfacial tension.

In addition, various governmental regulatory agencies in the UnitedStates have begun providing incentives for or simply mandating minimumbiodiesel blend components for commercial transportation fuels.Biodiesel is a blend of fatty acid methyl esters derived from causticcatalyzed methanol esterification of plant and animal triglycerides.Biodiesel is a surfactant, and fuel blends containing as little as 2%biodiesel have interfacial tensions well below 25 dynes/cm. As a result,the fuel pool available for non-gasoline transportation and powergeneration is rapidly transitioning to an interfacial tension regionwhere prior art fuel-water emulsion separation media fail to removewater from the hydrocarbon.

Despite shifts in fuel interfacial tension, water remains a fuelcontaminant of concern for corrosion of steel engine components andpromotion of microbiological growth. All non-gasoline engines havefuel-water separation capability mounted in the fuel system. Further,engine emission compliance with the EPA 2007 Highway Rule dependsheavily upon high pressure fuel injection equipment that is extremelysensitive to water. This makes fuel dewatering of higher importance forsystems designed to meet the 2007 EPA emission mandates that spawnedsystemic change in fuel quality. Fuel mileage and operator interfacerequirements for engines dictate the need for small, light, and easy tooperate water separation systems. These needs often preclude the complexseparation systems that are conventionally known. As a result, mandatedchanges in fuel quality have created a well defined need for a fibrous,porous coalescence media that removes water independent of hydrocarboninterfacial tension.

Examples of novel coalescence media are described in commonly-owned,co-pending U.S. patent application Ser. No. 12/014,864 filed on Jan. 16,2008 and entitled “Coalescence Media for Separation of Water-HydrocarbonEmulsions” (the entire content of which is expressly incorporatedhereinto by reference and will be referenced below as “the US '864application”). These media achieve high surface area with needed porestructure and permeability and effectively separate tenacious emulsionsof water and surfactant-containing hydrocarbons such as biodiesel-ULSDblends without use of complex separation systems. Media of the prior artoften require multiple layers to affect the single function ofseparation of water-hydrocarbon emulsions, without guarantee ofsuccessful separation in high surfactant content, low interfacialtension hydrocarbons. In contrast, the media described in U.S. patentapplication Ser. No. 12/014,864 is formed as single dry layer from awet-laid process using a homogenously distributed, wet-laid furnishincluding cellulose or cellulosic fibers, synthetic fibers,high-surface-area fibrillated fibers, glass microfiber, and asurface-area-enhancing synthetic material, which successfully performsthe single function of water separation with a single layer offiltration media in low interfacial tension hydrocarbons.

It is typical for any fibrous, porous coalescence media to be part of amulti-layered media structure where some of the layers perform functionsother than emulsion separation. In such cases, the layers may or may notbe laminated together. Reasons to employ multiple layers can be due tomedia integrity concerns and/or filtration needs. Relative to mediaintegrity, multiple layers are used to support the fibrous, porouscoalescence media or the composite structure, to protect the fibrous,porous coalescence media from high speed rotary pleaters, and to protectthe end use from possible migration of fibers from other media layers.Relative to filtration needs, multiple layers are used to add filtrationcapabilities such as particle removal, dirt holding, or impurityadsorption to coalescing performance. Impurities may consist ofasphaltenes, organic moieties, salts, ions, or metals. In order to meetfiltration goals as well as to protect media integrity, a layer on thedownstream side of the coalescing media in a multi-functional filtrationmedia is required.

Incorporation of a coalescing media into a multi-layered,multi-functional coalescing media structure with a layer on thedownstream side of the coalescing layer creates the possibility of mediafailure in high surfactant (i.e., sub-25 interfacial tension)hydrocarbons due to re-emulsification of the previously coalesced drops.In this regard, coalesced water drops must be large enough to settle outof the hydrocarbon flow by virtue of density differences otherwise theywill be carried out of the separating device with the dried hydrocarbonand re-emulsified therein. Coalescing media must therefore function toenlarge micron sized droplets of water found in high surfactant contentwater-hydrocarbon emulsions into millimeter sized coalesced water dropswhich can gravimetrically settle out of the dry hydrocarbon flow.

For the reasons noted above, in high surfactant content hydrocarbons,the performance of any coalescing layer in a multi-layered media can bedramatically reduced by media that is conventionally used on thedownstream side of the coalescing layer. Specifically, conventionalmedia situated on the downstream side of a coalescing layer includephenolic resin saturated cellulose wet laid media, polyester meltblown,spunbond, and meltblown-spunbond composites, and nylon spunbond. Suchconventional media can and does dramatically reduce the coalescingfunction of the coalescence media in high surfactant-containinghydrocarbons. By way of example, the performance reduction that can bemanifested through use of such conventional media downstream of acoalescing layer can be between about 50 to 100% of emulsified waterremaining in the hydrocarbon and thereby being passed on to thehydrocarbon's end use due to reduction in droplet size of the previouslycoalesced water droplets.

It would therefore be desirable if new media options to serve as layersplaced on the downstream side of a coalescing media could be providedthat perform requisite support and protection functions as well asdisplay sufficiently high surface area for water adsorption to minimizere-emulsification. In this regard, it would be especially desirable if amedia serving as a layer downstream of a coalescing layer perform notonly its traditional support and protection roles, but also provide fora higher surface area for water adsorption than the coalescing layer.Such a downstream layer would serve to expand the flow path available towater, and accordingly would induce the Venturi effect and reduce thewater velocity relative to the hydrocarbon. Such a velocity reductionwould in turn increase the water pressure within the downstream layer,thus forcing hydrocarbon out of the layer. These factors would serve tofurther separate water from hydrocarbon and thus facilitate furthercoalescence of the water. This is highly desirable for separationapplications involving surfactant-containing hydrocarbons. It istherefore additionally desirable to develop media capable of providingsupport and protection functions demanded of media placed on thedownstream side of a coalescing layer in a multi-layer coalescing mediathat provide higher surface area for water adsorption than availablewithin the coalescing layer.

It is towards fulfilling such desirable attributes that the presentinvention is directed.

SUMMARY OF EXEMPLARY EMBODIMENTS

According to one aspect, the embodiments disclosed herein provide forseparation media for separating water from a water and hydrocarbonemulsion comprising a fibrous nonwoven coalescence layer for receivingthe water and hydrocarbon emulsion and coalescing the water presenttherein as a discontinuous phase to achieve coalesced water dropletshaving a size of 1 mm or greater, and a fibrous nonwoven drop retentionlayer downstream of the coalescence layer having a high BET surface areaof at least 90 m²/g or greater sufficient to retain the size of thecoalesced water droplets to allow separation thereof from thehydrocarbon.

In certain preferred forms, the drop retention layer of the separationmedia will have a high BET surface area of at least 95 m²/g, morepreferably at least 100 m²/g, or greater.

The drop retention layer may comprise a mixture of fibers having a highBET surface area and fibers having a low BET surface area and/or maycomprise a resin binder. If a resin binder is provided, it mostpreferably includes a polar chemical group.

According to certain embodiments, the separation media may comprise atleast one additional layer positioned between the coalescence and dropretention layers. For example, at least one additional layer may bepositioned upstream and/or downstream of the drop retention layer toprovide the separation media with desired physical properties.

Modules for separating water from a water and hydrocarbon emulsion maybe provided having a housing provided with an inlet for the emulsion andrespective outlets for water and dewatered hydrocarbon, the housingbeing provided with a separation media therein. The separation mediaprovided in the housing preferably comprises a fibrous nonwovencoalescence layer for receiving the water and hydrocarbon emulsion andcoalescing the water present therein as a discontinuous phase to achievecoalesced water droplets having a size of 1 mm or greater, and a fibrousnonwoven drop retention layer downstream of the coalescence layer havinga high BET surface area of at least 90 m²/g or greater sufficient toretain the size of the coalesced water droplets to allow separationthereof from the hydrocarbon.

According to yet another aspect, the embodiments disclosed hereinprovide for methods to separate water from a water and hydrocarbonemulsion by passing a water and hydrocarbon emulsion through a fibrousnonwoven coalescence layer so as to coalesce the water present thereinas a discontinuous phase to achieve coalesced water droplets having asize of 1 mm or greater, and then passing the hydrocarbon and coalescedwater droplets though a downstream droplet retention layer having a highBET surface area of at least 90 m²/g or greater sufficient to retain thesize of the coalesced water droplets. The coalesced water droplets maythen be separated from the hydrocarbon (e.g., by the density differencestherebetween). Preferably at least 90 wt. % of the water in the emulsionis coalesced into water droplets having a size of 1 mm or greater by thecoalescence layer.

In preferred embodiments, the hydrocarbon has an interfacial tension (γ)of less than 25 dynes/cm (i.e., a sub-25 hydrocarbon). The hydrocarbonmay thus be a liquid fuel (e.g., a biodiesel fuel) which comprises asurfactant.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

These and other features and advantages will be better and morecompletely understood by referring to the following detailed descriptionof exemplary non-limiting illustrative embodiments in conjunction withthe drawings of which:

FIG. 1 is a schematic cross-sectional view of a water-hydrocarbonseparation system that embodies the separation media of the presentinvention; and

FIG. 2 is an enlarged schematic cross-sectional view of an exemplaryembodiment of the separation media according to the present invention astaken along line 2-2 in FIG. 1.

DEFINITIONS

As used herein and in the accompanying claims, the terms below areintended to have the definitions as follows.

A “water-hydrocarbon emulsion” is an emulsified mixture of immisciblewater and hydrocarbon liquids.

“Fiber” means a fibrous or filamentary strand of extreme or indefinitelength.

“Staple fiber” means a fiber which has been cut to definite, relativelyshort, segments of predetermined individual lengths.

“Fibrous” means a material that is composed predominantly of fiberand/or staple fiber.

“Non-woven” means a collection of fibers and/or staple fibers in a webor mat which are randomly mechanically interlocked and/or entangled withone another.

“Synthetic fiber” and/or “man-made fiber” refers to chemically producedfiber made from fiber-forming substances including polymers synthesizedfrom chemical compounds and modified or transformed natural polymer.Such fibers may be produced by conventional melt-spinning,solution-spinning and like filament production techniques.

A “natural fiber” is a fiber that obtained from animal, mineral orvegetable origins.

“BET surface area” means the surface area (m²) per unit weight (g) of asolid material calculated generally according to Brunauer-Emmett-Teller(BET) methodology as described more fully in S. Brunauer et al, J. Am.Chem. Soc., 1938, 60, 309 (the entire content of which is expresslyincorporated hereinto by reference), except that water vapor at 21° C.was employed. (See also the description of the Test Methods in theExamples below.)

“High BET” means a material having a BET surface area of 90 m²/g orgreater, more preferably a BET surface area of 95 m²/g or greater, andmost preferably a BET surface area of 100 m²/g or greater.

“Low BET” means a material having a BET surface area of less than 90m²/g.

A “sub-25 hydrocarbon” is a liquid hydrocarbon having an interfacialtension (γ) of less than 25 dynes/cm.

DETAILED DESCRIPTION

Accompanying FIG. 1 schematically depicts an exemplary module 10 thatembodies the present invention. In this regard, the module 10 isprovided with a housing 12 having an inlet 12-1 through which a liquidflow of a fuel and water emulsion can be introduced. The housing 12 alsoincludes outlets 12-2 and 12-3 to allow flows of dewatered (dry) fueland water, respectively, to be discharged from the housing followingseparation.

The housing 12 includes an interior space 12-4 for holding a separationmedia 14. In the embodiment depicted, the separation media 14 is in theform of a generally cylindrical structure comprised of a number oflongitudinally oriented pleats. Other structural forms of the separationmedia 14 are of course possible, for example, spirally wound sheets. Thefuel/water emulsion thus enters the core 14-1 of the media 14 and thenpasses therethrough. As is well known, due to density differences, thecoalesced water collects at the bottom of the housing and is dischargedtherefrom through the outlet 12-3. The dewatered (dry) fuel is in turndischarged through the outlet 12-2.

As is perhaps better shown in accompanying FIG. 2, the separation media14 is a multilayer structure comprised of at least a fibrous nonwovencoalescence layer 16 positioned upstream of a fibrous nonwoven dropretention layer 18. The coalescence layer 16 and the drop retentionlayer may be positioned immediately adjacent one another and may ifdesired be physically laminated or physically connected to one another(e.g., by any suitable technique known in the art such as needlepunching, adhesives, air jet entanglement and the like). Alternatively,one or more intermediate layers 20 may optionally be interposed betweenthe upstream coalescence layer 16 and the downstream drop retentionlayer 18. The various layers 16, 18 and optionally 20 may likewise bephysically adjacent one another or may be laminated or otherwiseconnected to one another by any suitable technique known in the art.

In addition (or alternatively) one or more face layers 22 may beprovided upstream of the coalescence layer 16, while one or more backinglayers 24 may be provided downstream of the drop retention layer 18.Layers 20, 22 and 24 are selected for various functional attributes anddo not necessarily need to be nonwoven structures. Of course, suchadditional layers 20, 22 and/or 24 must not affect adversely the dropretention functionality of the drop retention layer 18.

The coalescence media layer may be a single layer or a multi-layeredstructure. A preferred embodiment is a tri-layer structure having anupstream layer, a coalescing layer in an intermediate position, and adownstream drop retention layer. The drop retention layer may belaminated with the coalescing media layer into a single separation mediasheet. The upstream layer may be a filter layer or a second layer of thecoalescence media. The upstream layer of the media is preferablyprovided for particle filtration and/or to support the structure and/orto physically protect the drop retention layer 18. Tests indicated thenature of the upstream nonwoven exerted some influence over thecoalescing performance of the composite. Results reported here includesamples involving five separate upstream support layers. Upstream layerswere selected for maximized coalesced drop size and specific filtrationneeds, such as dirt holding capacity, asphaltene adsorption, andparticle removal efficiency.

The coalescence layer 16 of the separation media 14 may be of anysuitable type. In this regard, the coalescing layer is selected tocoalesce an aqueous discontinuous phase of the fuel and water emulsionon the order of 0.01-500 micrometers into discrete water droplets whichhave sizes of at least about 1 millimeter up to about 10 millimeters.This coalescence of the aqueous discontinuous phase into discrete waterdroplets occurs as the emulsion passes through the coalescing layer 16.

The coalescing layer 16 presents high surface area for adsorption ofwater, creating a longer path length for water than other emulsioncomponents. This difference in path length translates to differingelution times for water and other emulsion components, which results inphase enrichment and water coalescence. Separation of the water out ofthe emulsion occurs when coalesced aqueous drops gravimetrically settleout of the flow as it exits the downstream side of the media. Settlingoccurs because water is denser than hydrocarbons. In order to settleeffectively in a flowing system, coalesced water drops must oftenovercome the flow of purified hydrocarbon, which in many cases, iscounter to the motion of the drops. As such, the size of the water dropsis critical to the success of the coalescence media. Successfulseparation is favored by larger water drops. One particularly preferredmedia that may be employed satisfactorily as the coalescing layer 16 isdescribed in the US '864 application cited above.

The drop retention layer 18 is a fibrous nonwoven material that exhibitshigh BET surface area, that is a BET surface area that is at least 80%of 90 m²/g or greater, more preferably a BET surface area of 95 m²/g orgreater, and most preferably a BET surface area of 100 m²/g or greater.The principal function of the drop retention layer is to preventre-emulsification of the coalesced water droplets obtained by theupstream coalescence layer 16, especially for sub-25 hydrocarbons. Thus,after passing through the drop retention layer 18, the coalesced waterdroplets will retained their coalesced size of at least 1 mm or greater.In other words, the drop retention layer 18 will prevent sizedegradation of the coalesced water droplets achieved by the coalescencelayer 16.

In this regard, the drop retention layer can be formed of virtually anyfiber that possesses or can be modified to possess a high BET surfacearea. Particularly preferred for use as fibers to form the dropretention layers are natural fibers, such as cellulose orcellulose-based fibers (e.g., fibers of wood or plant origin), cottonfibers, wool fibers, silk fibers, rayon fibers and the like. Syntheticfibers formed of fiber-forming polymeric materials may also be employedsuch as fibers formed of polyesters, polyamides (e.g., nylon 6, nylon6,6, nylon 6,12 and the like), polyolefins, polytetrafluoroethylene, andpolyvinyl alcohol.

In certain embodiments, the drop retention layer 18 may be a mixture offibers having a high BET surface area and fibers having a low BETsurface area. In such embodiments, it is preferred that the high BETsurface area fibers be present in an amount of at least about 59 wt. %,more preferably at least about 65 wt. % of high BET surface area fibers,with the balance being low BET surface area fibers. Thus, the dropretention layer 18 will comprise between about 59 wt. % to 100 wt. %,preferably between about 65 wt. % to 100 wt. %, of high BET surface areafibers. However, it will be understood that such ranges are presentlypreferred embodiments of the invention since virtually any mixture ofhigh and low BET surface area fibers can be employed satisfactorilyprovided that the overall nonwoven media exhibits high BET surface areaproperties.

The drop retention layer 18 may optionally be provided with a binderresin so as to impart increased mechanical strength provided that theresin does not adversely affect the BET surface area of the nonwovendrop retention layer 18. If employed, it is preferred that the binderresin be one that possess a polar chemical group so as to facilitatewater adsorption and hence water separation from the emulsion. Suitablebinder resins that may be satisfactorily employed in the drop retentionlayer include, but are not limited to, phenolformaldehyde resins,polycarbonate resins, poly(acrylic acid) resins, poly(methacrylic acid)resins, polyoxide resins, polysulfide resins, polysulfone resins,polyamide resins, polyester resins, polyurethane resins, polyimideresins, poly(vinyl acetate) resins, poly(vinyl alcohol) resins,poly(vinyl chloride) resins, poly(vinyl pyridine) resins, poly(vinylpyrrolidone) resins, as well as copolymers and combinations or blendsthereof.

The drop retention layer may be apertured or patterned (embossed) usingtechniques well known to those in the art. Alternatively oradditionally, the drop retention layer may be treated by other suitabletechniques to achieve a form suitable for its intended end useapplication. By way of the example, the drop retention layer may becorrugated, creped, calendered, printed, micrexed and the like.

The basis weights of the coalescence layer 16 and the drop retentionlayers are not critical. Thus, the coalescence layer 16 and/or the dropretention layer 18 may have a basis weight of at least about 15 gramsper square meter (gsm), more preferably at least about 35 gsm up toabout 300 gsm. Some embodiments of the coalescence layer 16 may possessa basis weight of between about 35 up to about 110 gsm.

The optional intermediate layer(s) 20 and facing layers 22, 24 may beany sheet-like material that is chosen for a desired function. Forexample, the layers 20, 22 and/or 24 may be selected so as to provideparticulate filtration (e.g., so as to trap loose fibers and otherparticulate contaminants present in the liquid emulsion), in addition oralternatively to provide structural support and/or protection of thecoalescence layer 16 and/or drop retention layer 18. The layers 20, 22and/or 24 therefore need not be formed of a fibrous material but couldbe polymeric or metallic sheets or meshes that fulfill the desiredfunction. Suffice it to say that the skilled person in this art canenvision various multilayer structures that possess the desiredfunctional attributes for a given end use application provided thatwater is capable of being separated from a water and fuel emulsion.

The present invention will be further illustrated by the followingnon-limiting examples thereof.

Examples Test Methods

Adsorption isotherms used for application of BET method were determinedthrough gravimetric measurement of water uptake by each downstream layerusing the following procedure.

-   -   1. The interior of an inert atmosphere chamber was equilibrated        to constant relative humidity through exposure to a saturated        salt solution of known relative vapor pressure at a constant        temperature of 21° C. A milligram sensitive balance was kept        inside the chamber.    -   2. Samples of downstream layers were introduced to the chamber        and weighed daily until no change in weight was observed. This        typically took 1-2 weeks. Final weights of the samples were        recorded.    -   3. The saturated salt solution was replaced with a new solution        of different known relative humidity, and the        equilibration/weighing process repeated.    -   4. A total of five saturated salt solutions were used and are        shown with corresponding chamber relative humidity in the table        below.

Salt Solution Relative Humidity Lithium Chloride 0.16 Magnesium Chloride0.36 Potassium Carbonate 0.55 Sodium Bromide 0.64 Potassium Chloride0.88

-   -   5. At the conclusion of measurements for the fifth salt,        downstream layer samples were removed from the chamber and dried        in a 175° C. oven for five minutes and weighed.    -   6. Weight of adsorbed water on each sample at each relative        humidity was calculated from the difference of the sample weight        within the chamber at each relative humidity and the oven dried        sample weight.    -   7. Steps 1-6 were completed in triplicate for each downstream        layer sample.    -   8. In all cases, data obtained with Potassium Chloride produced        a nonlinearity in the BET plot, and was excluded from use in        surface area calculations.

Separation Media Testing

Tri-layer composites were tested as separation media for separatingwater from a liquid emulsion of water and hydrocarbon fuel and comprisedan upstream layer (UL), a coalescing layer (CL) and a downstream layer(DL) in that order relative to the flow direction of the emulsion. Themedia employed as the upstream layer (UL), the coalescing layer (CL) andthe downstream layer (DL) in the Examples are identified by the codes inTables 1, 2 and 3, respectively, below.

TABLE 1 Upstream Layer Codes Code Description UL1 TRINITEX ® wet laidtri-layer synthetic filtration media (Ahlstrom Corporation) UL2 Phenolicresin saturated cellulose-glass wet laid, high particle removalefficiency fuel filtration media (Ahlstrom Corporation) UL3 Hydrophobicphenolic resin saturated cellulose-glass wet laid, high particle removalefficiency fuel filtration/water separation media (Ahlstrom Corporation)UL4 Phenolic resin saturated cellulose-glass wet laid, asphlateneadsorption filtration media (Ahlstrom Corporation) UL5 Phenolic resinsaturated cellulose-glass wet laid, high capacity, high particle removalefficiency lube filtration media (Ahlstrom Corporation)

TABLE 2 Coalescing Layer Codes Code Description CL1 27.0 wt % B-Glass0.40 micron diameter; 44.1 wt % Virgin Softwood Kraft fiber; 18.3 wt. %fibrillated Lyocell cellulose fiber; 0.5 wt. % polyamide-epichlorohydrin(PAE) resin; and 0.2 wt. % polyacrylamide, 6% Lubrizol Hycar 26138modified acrylic polymer, 4% Alum CL2 30.0 wt % B-Glass 0.65 microndiameter; 49.0 wt % Virgin Softwood Kraft fiber; 20.3 wt. % fibrillatedLyocell cellulose fiber; 0.5 wt. % polyamide-epichlorohydrin (PAE)resin; and 0.2 wt. % polyacrylamide (Example 2 of US ′864 application)CL2P Same as Sample CL2 except produced on a paper machine instead oflaboratory equipment

TABLE 3 Downstream Layer Codes BET Basis Resin Surface DL Product WtAperture Furnish Components (%) Amt. Area Ident. Name (g/m²) PatternCellulose Rayon Lyocell PP PE Nylon Type (wt %) (m²/g) BH Ahlstrom 116none 100 — — — — — PF 22.5 89 2P-96 A Cerex 10 none — — — — — 100 — — 85Advanced Fabrics Cerex 23 E Fiberweb 17 none — — — — 100  — — — 3 Reemay2250 BC Ahlstrom 34 none — — — — 100  — — — 3 FF 34/1900 PBT PB SM BDJohns 42 none — — — — 100  — — — 9 Manville JM 6014011 BE Fiberweb 46none — — — — 100  — — — 5 Reemay 2016 BF Ahlstrom 80 none — — — — 100  —— — 36 25613 BG Cerex 102 none — — — — — 100 — — 76 Advanced FabricsSpectramax 102 D Ahlstrom 44 aperture — 100  — — — — Acrylic 16.3 167EX-180 (50%) + PVA (50%) AQ Ahlstrom 44 aperture — 100  — — — — Acrylic12 168 EX-182 (50%) + PVA (50%) AY Ahsltrom 61 24 mesh — — 70 — 30 — PVA1.2 114 SX-159 AZ Ahlstrom 61 FT-10 — 0-35 35-70 — 30 — PVA 2.2 113SX-555 V Ahlstrom 68 24 mesh — 0-35 35-70 — 30 — PVA 1.5 116 269 CAhlstrom 68 FT-10 — — 70 — 30 — PVA 2.0 127 268B J Ahsltrom 40 none —100  — — — — — — 206 SX-71 K Ahlstrom 40 none — — — — 100  — — — <1 SX-6L Ahlstrom 40 none — — 50 — 50 — — — 89 SX-441 M Ahlstrom 40 none — — 30— 70 — — — 51 SX-712 N Ahlstrom 40 none — — 65 — 35 — — — 109 SX-362 RAhlstrom 54 none — 70 — 30 — — — — 136 149075 S Ahlstrom 55 none —25-50  25-0  — 50 — — — 85 200 W Ahlstrom 55 none  80 20 — — — — — — 13911222 Y Ahlstrom 60 none — 80 — — 20 — — — 153 SX-329 AE Ahlstrom 78none — 70 — — 30 — — — 137 278 AG Ahlstrom 80 none — 60 — — 40 — — — 131SX-374 AH Ahlstrom 80 none — 80 — — 20 — — — 167 SX-371 AI Ahlstrom 80none — — — — 100  — — — 4 SX-220 AJ Ahlstrom 80 none — — 70 — 30 — — —119 SX-705 AK Ahlstrom 81 none — 100  — — — — — — 204 160020 AL Ahlstrom81 none — 100  — — — — — — 192 SX-55 AM Ahlstrom 81 none — 70 — — 30 — —— 133 140300 AN Ahlstrom 90 none — — 100  — — — — — 170 SX-602 AOAhlstrom 105 none — — 70 — 30 — — — 121 SX-617 AP Ahlstrom 107 none — —100  — — — — — 171 SX-570 Notes: PP = polypropylene PE = polyesterPF—phenol-formaldehyde PVA = polyvinyl acetate

The layers employed in the tri-layer composites tested were alsoselected for one or more functional attributes that are identified bythe function codes in Table 4 below:

TABLE 4 Function Code Description 1 Composite Support 2 ParticleFiltration 3 Water Coalescence 4 Drop Retention 5 Coalescence LayerProtection 6 End Use protection from Fiber Migration

Samples were tested in a flat sheet fuel-water separator bench test rigthat models the Society of Automotive Engineers (SAE) J1488 test. Thetest rig consisted of an emulsification loop and a test loop. 0.25%(2500 ppm) distilled deionized water was emulsified at 26-30° Celsiusinto fuel using a Gould's 1MC1E4CO Mechanically Coupled 0.75 kwcentrifugal pump (3.18 (i)×2.54 (o)×13.18 (imp.) cm) throttled to a flowrate of 7.6 LPM. The resulting fuel-water emulsion was flowed throughthe emulsification loop which passed the emulsion through a heatexchanger and a bank of clean-up filters before returning dry fuel backto the sump. In tests run in B40 (40% biodiesel/60% ULSD), fuel wasdried to 500-1500 ppm water using a bank of four conventional separatorfilters run in series.

A slip stream of emulsion was flowed from the emulsification loop intothe test loop. In the test loop, emulsion was passed through the flatsheet sample holder at a face velocity of 1.22 cm/min. Outlet from thesample holder was returned to the emulsification loop upstream of theheat exchanger. All upstream emulsion transfer lines were of diametersufficiently small to exceed SAE J1488 velocity targets. The test wasrun for 90 or 150 minutes with upstream/downstream and sump samplesdrawn on alternating 10 minute intervals.

The emulsion used in testing of the examples was Ultra Low Sulfur Diesel(ULSD) Type 2D from BP Products, NA, Naperville, Ill. Biodiesel wasmethylsoyate obtained from Renewable Energy Group, Ralston, Iowa. Theblend used was 40 weight percent biodiesel in ULSD. In keeping withindustry nomenclature, the resulting blend is identified as B40.Distilled water, 3.4 umho/cm, was Great Value bottled distilled, sodiumfree commercially available at Wal-Mart USA.

Emulsion samples were homogenized for at least one minute in a ColeParmer Ultrasonic Bath Model #08895-04. Water content was measured usinga Mettler Toledo Model D39 Karl Fischer titrator, and reported in partsper million (ppm). A metric ruler inside the downstream test chamber wasused to measure the size of water drops exiting the media.

Two performance metrics were used to judge the water separationcapability of a coalescing media, downstream water concentration andcoalesced water drop size. Downstream water concentration is determinedfrom Karl Fischer Titration of fuel samples collected in the acceptsflow from the downstream side of the multi-layered media. It measuresthe quantity of water in the fuel downstream of the coalescing layer inparts per million (ppm), based on mass. Clearly, lower levels oftitrated water correspond to better water removal performance. In thecase of downstream layer performance, however, downstream waterconcentration was a less important performance metric. This is the casebecause downstream layer work was conducted in B40 using an extremelyefficient coalescing layer. Water concentrations of 400-600 ppm aretypical in B40 blends with this coalescing layer. A downstream nonwovenlayer will not dramatically increase the water concentration expectedfor this coalescing layer. Also, Karl Fischer titrations in biodieselblends have significant variance. Typically, a downstream layer wasconsidered to have negative impact on downstream water concentrationwhen the titrated concentration rose above 800 ppm. Downstream waterconcentrations were measured at minutes 10 and 90 of the 90 minute testsreported here.

Success of any coalescing layer is dependent on coalesced water dropsgravimetrically falling out of a counter current of fuel on thedownstream side of the media. Many coalescing filter elements createhigh velocity fuel flow on the downstream side of the coalescingelement. Coalesced water drops must be large enough to settle out ofhigh velocity flow; otherwise they will be carried into the accepts, andre-entrained in the fuel. This re-entrainment constitutes failure of themedia to coalesce water, as water is found in Karl Fischer titrations ofdownstream fuel samples. As such, media that yield 1.0 mm drops arebetter coalescing media than those that produce 0.1 mm drops. Further,media that create 3.0 mm drops are better than those that create 1.0 mmdrops. Finally, media that create no drops, but yield a stream of waterflowing down the face of the media or down the center of the media, areconsidered to be the best, as no drops are available to be swept up inhigh speed fuel flow. Drops that are less than 1.0 mm in diameter arecalled “angels” in jet fuel applications. The presence of such angels onthe “dry side” of a jet fuel coalescing element is a sign of elementfailure.

Coalescence media have also traditionally been found to yield foam onthe downstream side. Foam production is detrimental to water separation.The foam consists of fuel-enriched water, and is less dense and morevoluminous than water. As a result it resists the compaction andsettling needed for successful water removal. Foam fills downstreamspaces and eventually is carried easily into the fuel accepts,re-entraining water in the fuel.

A drop size target of 1.0 mm and larger was set for the tri-layerlaminate media tested according to the examples. This limit was based oncoalesced water drop sizes of 1.0-1.7 mm routinely generated by thecoalescing layers used in the examples in the absence of a downstreamlayer. Persistent appearance of <1.0 mm drops and foam production wereconsidered failure characteristics. Absence of drops and creation of astream of water down the face of the media was considered a passcharacteristic as no drops were available to sweep into the accepts.Water drop size was measured using visual inspection at minutes 10 and90 of the 90 minute tests employed in the examples.

The testing results appear in Table 5 below.

TABLE 5

¹Upstream Layer codes defined in Table 1 ²Layer Function Codes definedin Table 4 ³Coalescing Layer codes defined in Table 2 ⁴LaminationMethods: 1= Layers pressed together with web adhesive on 20° C. hotplate; 2= layers and web adhesive tensioned over a curved surface with5.0 kg weight in 205° C. oven ⁵Downstream Layer media codes defined inTable 3 ⁷ Drop size was measured at minute 60, no data available forminute 90 ⁸Test performed in 20% biodiesel (B20), a less severe fuelblend as compared to B40 ⁹Titration performed at minute 30, no dataavailable for minute 10

As the data in Table 5 shows, those media in the downstream layer (DL)having a high BET surface area exhibited drop retention layerperformance characteristics. Specifically, the DL media having a BETsurface area of at least 90 m²/g or greater were sufficient to retainthe 1 mm or greater size of the water droplets coalesced by thecoalescing layer (CL).

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope thereof.

1. Separation media for separating water from a water and hydrocarbon emulsion comprising: a fibrous nonwoven coalescence layer for receiving the water and hydrocarbon emulsion and coalescing the water present therein as a discontinuous phase to achieve coalesced water droplets having a size of 1 mm or greater; and a fibrous nonwoven drop retention layer downstream of the coalescence layer having a high BET surface area of at least 90 m²/g or greater sufficient to retain the size of the coalesced water droplets to allow separation thereof from the hydrocarbon.
 2. The separation media of claim 1, wherein the drop retention layer has a high BET surface area of at least 95 m²/g or greater.
 3. The separation media of claim 1, wherein the drop retention layer has a high BET surface area of at least 100 m²/g or greater.
 4. The separation media of claim 1, wherein the drop retention layer comprises a mixture of fibers having a high BET surface area and fibers having a low BET surface area.
 5. The separation media of claim 1, wherein the drop retention layer comprises a resin binder.
 6. The separation media of claim 1, wherein the resin binder includes a polar chemical group.
 7. The separation media of claim 1, which further comprises at least one additional layer adjacent to one of the coalescence and drop retention layers.
 8. The separation media of claim 7, wherein the at least one additional layer is positioned between the coalescence and drop retention layers.
 9. The separation media of claim 7, wherein the at least one additional layer is positioned upstream of the coalescence layer.
 10. The separation media of claim 7, wherein the at least one additional layer is positioned downstream of the drop retention layer.
 11. A separation module for separating water from a water and hydrocarbon emulsion comprising a housing having an inlet for the emulsion and respective outlets for water and dewatered hydrocarbon, and a separation media according to claim 1 within the housing.
 12. A method for separating water from a water and hydrocarbon emulsion comprising: (a) passing a water and hydrocarbon emulsion through a fibrous nonwoven coalescence layer so as to coalesce the water present therein as a discontinuous phase to achieve coalesced water droplets having a size of 1 mm or greater; and (b) passing the hydrocarbon and coalesced water droplets through a downstream droplet retention layer having a high BET surface area of at least 90 m²/g or greater sufficient to retain the size of the coalesced water droplets; and (c) separating the coalesced water droplets from the hydrocarbon.
 13. The method of claim 12, wherein the hydrocarbon has an interfacial tension (γ) of less than 25 dynes/cm.
 14. The method of claim 13, wherein the hydrocarbon is a liquid fuel which comprises a surfactant.
 15. The method of claim 14, wherein the liquid fuel is a fuel which comprises biodiesel.
 16. The method of claim 12, wherein step (a) is practiced so that at least 90 wt. % of the water in the emulsion is coalesced into water droplets having a droplet size of 1 mm or greater.
 17. The method of claim 16, wherein step (b) is practiced so that the coalesced water droplets retain a droplet size of 1 mm or greater.
 18. The method of claim 12, wherein step (c) is practiced by allowing the water droplets to separate from the hydrocarbon by a density difference therebetween. 